This investigation is concerned with the preparation of structurally different 13C labeled barbituric acid derivatives and the measurement of 13C-nmr chemical shifts, 13C spin lattic relaxation times, and NOE parameters of these compounds in various solvent media. The measurement of the same 13C-nmr parameters will also be carried out on selected barbiturates complexed with adenine derivatives. The main goal of these studies will be to learn more about the conformational differences and the binding capabilities of the different barbiturates and thus to learn about the molecular basis of the biological effects of these drugs.